worker_thread_ticker.h

// Copyright (c) 2009 The Chromium Authors. All rights reserved.// Use of this source code is governed by a BSD-style license that can be// found in the LICENSE file.#ifndef CHROME_COMMON_WORKER_THREAD_TICKER_H_#define CHROME_COMMON_WORKER_THREAD_TICKER_H_#include <vector>#include "base/lock.h"#include "base/thread.h"// This class provides the following functionality:// It invokes a set of registered handlers at periodic intervals in// the context of an arbitrary worker thread.// The timer runs on a separate thread, so it will run even if the current// thread is hung. Similarly, the callbacks will be called on a separate// thread so they won't block the main thread.class WorkerThreadTicker {
public:
// This callback interface to be implemented by clients of this// classclass Callback {
public:
// Gets invoked when the timer period is upvirtualvoid OnTick() = 0;
protected:
virtual ~Callback() {}
};
// tick_interval is the periodic interval in which to invoke the// registered handlers (in milliseconds)explicit WorkerThreadTicker(int tick_interval);
~WorkerThreadTicker();
// Registers a callback handler interface// tick_handler is the handler interface to register. The ownership of this// object is not transferred to this class.bool RegisterTickHandler(Callback *tick_handler);
// Unregisters a callback handler interface// tick_handler is the handler interface to unregisterbool UnregisterTickHandler(Callback *tick_handler);
// Starts the ticker. Returns false if the ticker is already running// or if the Start fails.bool Start();
// Stops the ticker and waits for all callbacks. to be done. This method// does not provide a way to stop without waiting for the callbacks to be// done because this is inherently risky.// Returns false is the ticker is not runningbool Stop();
bool IsRunning() const {
return is_running_;
}
void set_tick_interval(int tick_interval) {
tick_interval_ = tick_interval;
}
int tick_interval() const {
return tick_interval_;
}
private:
class TimerTask;
void ScheduleTimerTask();
// A list type that holds all registered callback interfacestypedef std::vector<Callback*> TickHandlerListType;
// Lock to protect is_running_ and tick_handler_list_
Lock lock_;
base::Thread timer_thread_;
bool is_running_;
// The interval at which the callbacks are to be invokedint tick_interval_;
// A list that holds all registered callback interfaces
TickHandlerListType tick_handler_list_;
DISALLOW_COPY_AND_ASSIGN(WorkerThreadTicker);
};
#endif // CHROME_COMMON_WORKER_THREAD_TICKER_H_